Date: Thu, 03 Jul 2008 08:27:40 -0700 From: Nate Lawson <nate@root.org> To: David Wolfskill <david@catwhisker.org> Cc: acpi@freebsd.org Subject: Re: How/why would dev.cpu.0.freq_levels change??!? Message-ID: <486CEFEC.2070107@root.org> In-Reply-To: <20080627235319.GP70792@bunrab.catwhisker.org> References: <20080627235319.GP70792@bunrab.catwhisker.org>
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David Wolfskill wrote: > My laptop is a Dell Inspiron 8200; I (ab)use it moderately heavily: > this includes tracking RELENG_6, RELENG_7, & HEAD on it, daily. > > Lately there have been some times when "make buildworld" for RELENG_6 > has taken a lot longer than it used to ... and I noticed that the > fans were on, even though it was running fairly cool (around 50C; > during a "make buildworld, around 85C is more common) -- and that > the machine was typically "topping out" at half speed (1200 MHz). > > During these times, querying dev.cpu.0.freq_levels would yield a list > that did, ini fact, max out at 1200 MHz, when I know that it has gone up > to 2400 MHz in the past. The ACPI spec describes how the _PSS levels can change dynamically at runtime. For instance, if you go off AC, the system might offer a lower power state. I'm guessing you're using the acpi_perf driver. Usually the system generates a notify when that happens though so I was surprised there was no dmesg. I'm not sure how well we support changing levels yet. -- Nate
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